Voltage pump circuits, which are voltage-multiplier circuits, are needed in embedded dynamic random access memory (EDRAM) and other integrated circuits, for example, to drive wordlines and provide boosted supply nodes for high-voltage applications. High-voltage oxide stress, for example, excessive transistor gate-to-source voltage, within the voltage pump circuit can cause a reliability problem when high-performance thin-oxide devices are used. Thicker oxide devices could be used in order to avoid voltage stress problems, but thick-oxide devices may not be available in the technology menu of, for example, cost sensitive EDRAM designs. Diode circuits have been used in the rectifying path of voltage pump circuits instead of switched devices in order to avoid stress problems, but the use of series diodes reduces the high-voltage output of the voltage pump by a diode voltage (Vbe) or by a field-effect transistor threshold voltage (FET-Vt), which is unacceptable.
A need exists for a voltage pump circuit that has an oxide stress control mechanism, in order to ensure a safe transistor gate-to-source voltage in high-voltage applications in an integrated circuit.